A lesson I have learned the hard way is that we aren’t smart enough. Even the most brilliant programmers routinely make stupid mistakes. Not just typos, but basic design errors that back the code into a corner, and in retrospect should have been obvious. […] I find it immensely helpful to work on the assumption that I am too stupid to get things right. This leads me to conservatively use what has already been shown to work, to cautiously test out new ideas before committing to them, and above all to prize simplicity.